This invention relates to a height adjustment mechanism for a chair and to a method for retrofitting a chair with such a height adjustment mechanism.
The seat of an office chair is typically supported on a gas cylinder having two-chambers separated by a normally closed valve. Such a gas cylinder generally terminates in a valve opening member at its top end, which valve opening member is biased to an extended position whereat the valve is closed. A user actuator is supplied to depress the valve opening member in order to open the cylinder valve to permit height adjustment of the seat. A known user actuator comprises a rod which terminates in a paddle tiltably mounted in a housing above the valve opening member. With such an actuator, the user may depress the valve opening member by raising the paddle. Such an actuator may be unsightly and awkward to reach.
U.S. Pat. No. 5,577,804 to Tedesco describes a height adjustment mechanism with a lever arm pivotably mounted to a housing above the valve opening member and a support arm rigidly extending below the lever arm. A co-axial cable has its inner wire attached to the lever arm and its outer sheath supported by the support arm. The other end of the cable terminates in a button which may be mounted under the seat or to the chair armrest. By pressing the button, the user may adjust the seat height. While this arrangement avoids problems attendant with a paddle actuator, it still leaves many existing chairs with such actuators.
This invention seeks to overcome drawbacks of existing chair height adjustment mechanisms.